Abstract:

To deeply research and disclose change rules of flood and sediment series at the middle reach of the Yellow River from stochastic aspect macroscopically, a joint distribution model of flood and sediment was constructed with Copula function method and then its application was discussed, based on the time series of flood peak flow that over 6 000 m³/s and its corresponding peak sediment concentration during a flood course from 1952 to 1998 of the Tongguan gauge at the middle reach of the Yellow River. The results show that among the synchronous encounter probabilities of rich-poor state between flood and sediment, the synchronous rich probability is appreciably greater than the synchronous poor probability and the synchronous common probability is the smallest, their values are 25.61%, 24.14% and 8.61% respectively; among the asynchronous encounter probabilities of the rich-poor state between flood and sediment, the probability that flood is common (poor) and sediment is poor (common) is 8.93%, the probability that flood is rich (common) and sediment is common (rich) is 7.46%, and the probability that flood is rich (poor) and sediment is poor (rich) is the smallest, which is 4.43%; and the same recurrence period can correspond to different combination events between flood and sediment. The construction and application of the joint distribution model achieved coupled evaluation and integrated appraisement of flood and sediment during a flood course.

Key words: Yellow River, flood season, flood course, flood and sediment, Copula function